Typically, an enhanced ground proximity warning system (EGPWS) must rapidly determine if EGPWS created objects are to be displayed on a display that may have overlaid polygons, thereby reducing the available area of the display. The easiest method for defining the available area is through the creation of a bitmap (i.e., white is inside/black is outside). However, the present method, which uses triangles to define the area, can not perform this in real-time while the aircraft is in flight. Therefore, a real-time drawing method is needed.